Melt-spun polyamide 56 fully drawn yarn and method of making same

Abstract

The application provides a melt direct spinning polyamide 56 fully drawn yarn and a preparation method thereof. Through optimization of a melt direct spinning process, a large-capacity high-performance bio-based polyamide 56 fully drawn yarn is prepared, production is stable, there are few floating single filaments and injection head filaments, the fiber production rate is high, and the mechanical properties and dyeing properties are excellent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyamide materials, and particularly relates to a melt direct spinning polyamide 56 fully drawn yarn and a preparation method thereof. BACKGROUND

[0002] Melt spinning is one of the main forming methods of synthetic fibers, which is also called melt spinning. Melt spinning is divided into direct spinning and chip spinning. Direct spinning is to directly send the polymer melt after polymerization to spinning; chip spinning needs to send the polymer solution to spinning after casting, granulating and drying and other pre-spinning preparation processes.

[0003] The monomer content in the polymer of polyamide 6 is relatively high (about 10 wt%), and the chip needs to be extracted before melt spinning can be realized. At present, melt direct spinning cannot be industrialized. In the spinning process of polyamide 66, gel is easily produced, dyeing is difficult, and other problems, and great difficulties are faced in the melt direct spinning technology of civil silk. Although melt direct spinning has been partially realized in the field of industrial silk, the melt conveying pipeline and the spinning box need to be regularly disassembled, calcined and cleaned, which increases the spinning cost.

[0004] Patent No. CN105669969 B discloses a nylon 6 polymerization method and a melt direct spinning method. The nylon 6 prepolymer is prepared at a low temperature, the oligomer content in the melt is pre-controlled, then the polymerization is completed before the generation of a large amount of cyclic oligomers through the method of kinetic strengthening of polycondensation reaction, and a nylon 6 polymer melt with a certain molecular weight is obtained. The extractable content in the obtained product is ≤1.5 wt%, and the cyclic dimer content is ≤0.2 wt%. Then, the melt spinning is directly formed after the end of the kinetic strengthening of polycondensation reaction, but there is still no technical breakthrough and industrialization case.

[0005] Patent No. CN103668510 A discloses a device and a method for producing fine or ultrafine nylon 66 filaments. The device includes an evaporator, a preheater, a reactor, a flash evaporator and a post-polycondensation system. After the polycondensation reaction of the nylon 66 salt aqueous solution, the nylon 66 melt is obtained, and then the nylon 66 melt is directly spun to prepare fine or ultrafine nylon 66 POY filaments. The spinning speed is 4200-4300 m / min, the spinning speed is low, the yield is low, and the fiber strength is low.

[0006] The bio-based polyamide 56 uses bio-based pentanediamine as a monomer raw material. The carbon emission of the bio-based polyamide 56 per unit weight is reduced by more than 50% compared with the carbon emission of nylon 66 and nylon 6 of the same weight. The popularization and application of the bio-based polyamide 56 will have a positive effect on improving the dependence on imported key materials in China and is of great significance to the sustainable development of solving the dependence on fossil resources and low-carbon emission reduction. The bio-based polyamide 56 material has excellent mechanical properties, moisture absorption and quick drying, skin friendliness, wear resistance, good softness, and low-temperature easy dyeing characteristics, and has a wide application prospect in the fields of civil filaments, staple fibers, industrial filaments, continuous bulk long filaments, monofilaments and the like. However, there is no related research and report on the industrialized preparation of large-capacity bio-based polyamide 56 fully drawn yarn by melt direct spinning at present. SUMMARY

[0007] In order to realize the industrialized production requirements of the bio-based polyamide 56 melt direct spinning, the bio-based polyamide 56 fully drawn yarn with large capacity and high performance is prepared by optimizing the melt direct spinning process, the production is stable, the number of floating monofilaments and injection head filaments is small, the fiber production rate is high, and the mechanical properties and dyeing properties are excellent.

[0008] A first object of the present application is to provide a melt direct spinning polyamide 56 fully drawn yarn, the fineness of the melt direct spinning polyamide 56 fully drawn yarn is ≤300 dtex; and / or,

[0009] The yarn evenness of the melt direct spinning polyamide 56 fully drawn yarn is ≤1.0%, for example, 0.7-0.95%, preferably ≤0.9%, further preferably ≤0.8%, and more preferably ≤0.7%; and / or,

[0010] The breaking strength of the melt direct spinning polyamide 56 fully drawn yarn is 4.0-8.0 cN / dtex; the breaking strength variation coefficient (CV) % is ≤4%, preferably ≤3.5%, further preferably ≤3.0%, and more preferably ≤2.5%; and / or,

[0011] The elongation at break of the melt direct spinning polyamide 56 fully drawn yarn is ≤55%, preferably ≤50%, further preferably ≤48%, and more preferably ≤45%, for example, 40-45%; the elongation at break variation coefficient (CV) % is ≤4.5%, preferably ≤4.0%, further preferably ≤3.5%, and more preferably ≤3.0%; and / or,

[0012] The initial modulus of the melt direct spinning polyamide 56 fully drawn yarn is 15-45 cN / dtex; and / or,

[0013] the boiling water shrinkage of the melt-spun polyamide 56 fully drawn yarn is ≤ 13 %, preferably ≤ 12.5 %, further preferably ≤ 12 %, still further preferably ≤ 11 %, such as 9-11 %; and / or,

[0014] the dyeing uniformity (grey card) of the melt-spun polyamide 56 fully drawn yarn is ≥ 3.5 grade, preferably ≥ 4.0 grade, further preferably ≥ 4.5 grade, still further preferably ≥ 4.7 grade; and / or,

[0015] the dyeing double A rate of the melt-spun polyamide 56 fully drawn yarn is ≥ 96 %, preferably ≥ 97 %, further preferably ≥ 98 %, still further preferably ≥ 99 %; and / or,

[0016] the cake appearance double A rate of the melt-spun polyamide 56 fully drawn yarn is ≥ 96 %, preferably ≥ 97 %, further preferably ≥ 98 %, still further preferably ≥ 99 %.

[0017] In some specific embodiments, the denier is for example 10-200 dtex, or 10-150 dtex.

[0018] In some specific embodiments, the breaking strength is for example 4.3-7.0 cN / dtex, or 4.5-6.2 cN / dtex, or 4.7-5.8 cN / dtex.

[0019] In some specific embodiments, the initial modulus is for example 20-43 cN / dtex, or 25-40 cN / dtex, or 30-39 cN / dtex.

[0020] A second object of the present application is to provide a process for preparing the melt-spun polyamide 56 fully drawn yarn, which comprises at least the following steps: polyamide 56 melt is passed through a melt booster pump, a melt filter, a melt delivery pipe to a spinning beam, to form a nascent yarn, which is cooled, oiled, drawn, heat set, and wound to obtain the melt-spun polyamide 56 fully drawn yarn;

[0021] When the polyamide 56 melt is a bright melt, the titanium dioxide content thereof is 0; when the polyamide 56 melt is a semi-dull melt, the titanium dioxide content thereof is 0.25-0.35 wt %, further preferably 0.28-0.33 wt %.

[0022] In some specific embodiments, the relative viscosity of the polyamide 56 melt is 2.4-3.0, preferably 2.45-2.9, more preferably 2.5-2.85, still more preferably 2.55-2.8.

[0023] In some embodiments, the polyamide 56 melt has an end amino group content of 30-120 mmol / kg, preferably 35-100 mmol / kg, more preferably 40-80 mmol / kg, and further preferably 45-60 mmol / kg.

[0024] In some embodiments, the polyamide 56 melt has an equilibrium moisture content of 200-1000 ppm, preferably 300-900 ppm, more preferably 350-850 ppm, and further preferably 400-800 ppm.

[0025] In some embodiments, the method for preparing the polyamide 56 melt comprises the steps of preparing a polyamide 56 salt solution from pentanediamine, adipic acid and water, and then pre-polymerizing, flashing, and polycondensing to obtain the polyamide 56 melt.

[0026] In some embodiments, the molar ratio of the pentanediamine to adipic acid is (1-1.09):1.

[0027] In some embodiments, the polyamide 56 salt solution has a concentration of 40-80 wt%.

[0028] In some embodiments, the polyamide 56 salt solution has a pH value of 6.0-9.2, and further 7.3-8.6.

[0029] In some embodiments, the pre-polymerization is performed at a pressure of 1.0-2.6 MPa, preferably 1.2-2.4 MPa, further preferably 1.4-2.2 MPa, and more further preferably 1.6-2.0 MPa, and at a temperature of 160-270℃, preferably 180-265℃, further preferably 200-260℃, and more further preferably 220-255℃.

[0030] In some embodiments, the polycondensation is performed at a pressure of -(0-0.09) MPa, preferably -(0.01-0.08) MPa, further preferably -(0.02-0.07) MPa, and more further preferably -(0.03-0.06) MPa, and at a temperature of 260-290℃, preferably 265-288℃, further preferably 270-286℃, and more further preferably 273-283℃.

[0031] In some embodiments, when the polyamide 56 melt is a semi-dull melt, the dispersed particle size of the titanium dioxide in the polyamide 56 melt is controlled to be 0.1-0.6 μm, preferably, the proportion of particles with a titanium dioxide dispersed particle size of 0.2-0.4 μm is more than 95%; more preferably, the proportion of particles with a titanium dioxide dispersed particle size of 0.2-0.3 μm is more than 90%.

[0032] In some embodiments, the titanium dioxide is added in the flash process.

[0033] In some embodiments, the residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 10-50 min, preferably 13-40 min, further preferably 16-35 min, and more further preferably 18-30 min.

[0034] In some embodiments, the temperature of the melt delivery pipe is controlled to be 260-290°C, preferably 265-288°C, further preferably 270-286°C, and more further preferably 273-284°C.

[0035] In some embodiments, the dynamic viscosity of the polyamide 56 melt is controlled to be ≥ 160 pa*s, preferably ≥ 180 pa*s, further preferably ≥ 200 pa*s, and more further preferably ≥ 220 pa*s from the melt booster pump to the spinning beam.

[0036] In some embodiments, the pressure of the monomer suction device is controlled to be ≥ 0.6 MPa, further ≥ 0.65 MPa, and more further ≥ 0.7 MPa.

[0037] In some embodiments, the polyamide 56 melt is delivered to the spinning beam through a melt pipe, accurately metered by a metering pump, and injected into a spinning assembly to form a nascent fiber from a spinneret.

[0038] In some embodiments, the number of holes of the spinneret is 7-272 f.

[0039] In some preferred embodiments, a saturated superheated steam device and a monomer suction device are arranged below the spinning beam.

[0040] The inventor sprays the saturated superheated steam from all around below the spinneret, and the polyamide oligomer overflowing from the spinneret holes and the fiber surface is dissolved in the saturated superheated steam and then carried away by the monomer suction device, keeping the spinneret and below clean, prolonging the spinneret plate cycle, reducing the injection head yarn and broken filament phenomenon caused by oligomers in the spinning process, and effectively improving the spinning production stability and yield.

[0041] In some embodiments, the temperature of the saturated superheated steam device is controlled to be 90-250°C, further 120-230°C, and more further 130-200°C.

[0042] In some embodiments, the pressure of the saturated superheated steam device is controlled to be 0.8-3.2 bar, further 1.0-2.8 bar, and more further 1.2-2.5 bar.

[0043] In some embodiments, the pressure of the monomer suction device is controlled to be ≥0.6 MPa, further ≥0.65 MPa, and more further ≥0.7 MPa.

[0044] In some embodiments, the drawing process uses 2 pairs or more of drawing rollers, preferably 2 pairs of drawing rollers, i.e. the oiling nascent yarn is first fed into G1 drawing rollers, and then drawn and heat set between G2 drawing rollers and G1 drawing rollers.

[0045] In some embodiments, the G1 drawing roller speed is 1800-4200 m / min, preferably 2300-3900 m / min, and more preferably 2800-3600 m / min.

[0046] In some embodiments, the G2 drawing roller speed is 4500-5500 m / min, preferably 4600-5300 m / min, and more preferably 4700-5200 m / min.

[0047] In some embodiments, the draw ratio is 1.25-2.5, preferably 1.3-2.0, and more preferably 1.35-1.8.

[0048] In some embodiments, the heat setting temperature is 140-180°C, preferably 145-175°C, and more preferably 150-170°C.

[0049] In some embodiments, the winding speed is ≥4500 m / min, preferably ≥4600 m / min, more preferably ≥4700 m / min, and further preferably ≥4800 m / min.

[0050] In some embodiments, the breaking filament frequency of the polyamide 56 fully drawn yarn is ≤2 / 1 spinning position 24 h, preferably ≤1 / 1 spinning position 24 h, and more preferably ≤0 / 1 spinning position 24 h.

[0051] In some specific embodiments, the polyamide 56 fully drawn yarn has a production rate of ≥ 97%, preferably ≥ 97.5%, further preferably ≥ 98%, and more preferably ≥ 98.5%.

[0052] The melt direct spinning polyamide 56 fully drawn yarn provided by the present application can be applied in the fields of underwear, shirts, suits, yoga clothes, down jackets, outdoor jackets, socks, bags, curtains, shoe materials, embroidery threads, trademarks, sand publications, work clothes, sportswear, elastic bands, etc.

[0053] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining preferred examples of the present application. The reagents and raw materials used in the present application are commercially available.

[0054] The positive progress effect of the present application is that:

[0055] First, the production raw material 1,5-pentanediamine of the polyamide 56 fully drawn yarn provided by the present application is made by a biological method, which is a green material, does not depend on petroleum resources and does not cause serious pollution to the environment, and can reduce the emission of carbon dioxide and the generation of greenhouse effect, thereby adapting to the development trend of carbon neutralization.

[0056] Second, by using the preparation method of the melt direct spinning polyamide 56 fully drawn yarn provided by the present application, through optimizing the melt direct spinning process, controlling the parameters such as melt residence time, melt conveying temperature and dynamic viscosity of the melt, not only the production of large-capacity polyamide 56 fully drawn yarn can be realized, but also the gel content in the melt booster pump to the spinning box can be effectively reduced.

[0057] Specifically, the annual output of the melt direct spinning polyamide 56 fully drawn yarn can reach 10-50 thousand tons per line, preferably 20 thousand tons per line; the spinning position can be 192 positions per line, 144 positions per line, 120 positions per line or 96 positions per line or below; the number of spinning heads can be 8-24 heads per position, preferably 12-24 heads per position. The preparation method provided by the present application saves the steps of melt granulation, chip drying and screw melting in the chip spinning process, thereby greatly reducing the production cost of the polyamide 56 fully drawn yarn. The gel content can be controlled to be ≤ 1.5 wt% per 6 months, preferably ≤ 1.2 wt% per 6 months, more preferably ≤ 1.0 wt% per 6 months, and further preferably ≤ 0.7 wt% per 6 months. The reduction of the gel content greatly reduces the number of times of disassembling, calcining and cleaning the melt pipeline and the spinning box, thereby reducing the production cost.

[0058] Third, the melt direct spinning polyamide 56 fully drawn yarn provided by the present application has stable production, less single yarn and injection head yarn, high fiber production rate, and excellent mechanical properties and dyeing performance. DETAILED DESCRIPTION

[0059] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application. The experimental methods not specified in the following embodiments are selected according to the conventional methods and conditions or the product instructions.

[0060] Test method:

[0061] (1) Relative viscosity: by Ubbelohde viscometer concentrated sulfuric acid method: accurately weigh 0.25±0.0002g of polyamide melt sample after drying online, add 50mL of concentrated sulfuric acid (96wt%), dissolve; measure and record the concentrated sulfuric acid flow time t0 and the polyamide sample solution flow time t in a 25℃ constant temperature water bath. The viscosity number calculation formula: relative viscosity=t / t0; t-solution flow time; t0-solvent flow time.

[0062] (2) Amino terminal: determined according to automatic titrator.

[0063] (3) Moisture content: determined according to Karl Fischer moisture titrator.

[0064] (4) Fineness: determined according to GB / T 14343.

[0065] (5) Yarn evenness: yarn evenness refers to the degree of thickness variation of yarn along its length direction, including yarn appearance diameter unevenness and linear density unevenness, and the detection equipment is Uster evenness tester.

[0066] (6) Breaking strength, breaking strength variation coefficient (CV) %, breaking elongation, breaking elongation variation coefficient (CV) %: determined according to GB / T 14344-2008 chemical fiber fiber tensile property test method; 0.05±0.005cN / dtex pre-tension is applied, holding distance is 250mm, and the tensile speed is 1000mm / min.

[0067] (7) Initial modulus: determined according to GB / T 14344-2008.

[0068] (8) Boiling water shrinkage: determined according to GB / 6505-2008.

[0069] (9) Dyeing uniformity (grey card) / grade: determined according to FZ / T 50008 polyamide filament dyeing uniformity test method.

[0070] (10) Dyeing double A rate: Dyeing double A rate = ((weight of fibers with dyeing evenness of ≥ 4.5 grade) / total weight of all dyed fibers) x 100%.

[0071] (11) Yarn cake appearance double A rate: Artificially judged.

[0072] (12) Broken filament frequency: Artificially counted.

[0073] (13) Production rate: Production rate = (mass of prepared finished fibers / total mass of polyamide melt input) x 100%.

[0074] (14) Gel content: Randomly select 6 melt samples from 6 melt conveying pipelines after 6 months of line operation, measure and take the average value according to the following method, take the mass of the cooled and dried melt sample as A1, use Soxhlet extraction method for reflux extraction, take out the sample and dry, take the mass of the sample in the filter paper bag as A2, the calculation formula of the gel content is: gel content wt% = A2 / A1*100%.

[0075] Example 1: 44 dtex / 34 f melt direct spinning polyamide 56 fully drawn yarn

[0076] (1) prepare a polyamide 56 salt solution from pentanediamine, adipic acid and water, then obtain a polyamide 56 melt through pre-polymerization, flashing and polycondensation;

[0077] wherein the molar ratio of the pentanediamine and adipic acid is 1.08:1; the concentration of the polyamide 56 salt solution is 52 wt%; the pH value of the polyamide 56 salt solution is 7.8;

[0078] the pressure of the pre-polymerization is 1.6 Mpa and the temperature is 250℃;

[0079] the pressure of the polycondensation is -0.05 Mpa and the temperature is 278℃;

[0080] the polyamide 56 melt is a bright melt, and the titanium dioxide content thereof is 0;

[0081] the relative viscosity of the polyamide 56 melt is 2.45; the end amino group content is 45 mmol / kg; and the equilibrium moisture content is 450 ppm.

[0082] (2) the polyamide 56 melt obtained in step (1) is conveyed to a spinning beam through a melt booster pump, a melt filter and a melt conveying pipeline to form a nascent yarn, and the nascent yarn is cooled, oiled, drawn, heat set and wound to obtain a melt direct spinning polyamide 56 fully drawn yarn;

[0083] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 20 min; the temperature of the melt conveying pipeline is controlled at 275℃; the dynamic viscosity of the polyamide 56 melt is controlled at 220 pa*s from the melt booster pump to the spinning beam;

[0084] The temperature of the spinning beam is 275℃; the spinning assembly pressure of the spinning beam is 12 MPa.

[0085] A saturated superheated steam device and a monomer suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled at 150℃, the pressure of the saturated superheated steam device is controlled at 1.5 bar, and the pressure of the monomer suction device is controlled at 0.65 MPa;

[0086] The drawing process adopts 2 pairs of drawing rollers, and the oiled nascent yarn is first fed into the G1 drawing roller, and then drawn and heat set between the G2 drawing roller and the G1 drawing roller, wherein the G1 drawing roller speed is 3000 m / min; the G2 drawing roller speed is 4800 m / min; the draw ratio is 1.6; the heat setting temperature is 165℃; and the winding speed is 4780 m / min.

[0087] The annual output of the melt direct spinning polyamide 56 fully drawn yarn in the embodiment can reach 12,000 tons per line, the spinning position is 48 positions per line, and the number of spinning heads is 24 per position.

[0088] Example 2: 55 dtex / 48 f melt direct spinning polyamide 56 fully drawn yarn

[0089] (1) pentanediamine, adipic acid and water are used to prepare a polyamide 56 salt solution, and then pre-polymerization, flashing and polycondensation are performed to obtain a polyamide 56 melt;

[0090] The molar ratio of the pentanediamine and the adipic acid is 1.06:1; the concentration of the polyamide 56 salt solution is 55 wt%; and the pH value of the polyamide 56 salt solution is 7.9;

[0091] The pre-polymerization pressure is 1.65 MPa, and the temperature is 253℃;

[0092] The polycondensation pressure is -0.06 MPa, and the temperature is 275℃;

[0093] The polyamide 56 melt is a bright melt, and the titanium dioxide content is 0;

[0094] The relative viscosity of the polyamide 56 melt is 2.50; the end amino group content is 48 mmol / kg; and the equilibrium moisture content is 400 ppm.

[0095] (2) the polyamide 56 melt obtained in step (1) is subjected to a melt booster pump, a melt filter, a melt delivery pipe to a spinning beam, to form a nascent yarn, which is subjected to cooling, oiling, drafting, heat setting, and winding, to obtain a melt-spun polyamide 56 fully-drawn yarn;

[0096] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 20 min; the temperature of the melt delivery pipe is controlled to be 276°C; the dynamic viscosity of the polyamide 56 melt is controlled to be 230 pa*s from the melt booster pump to the spinning beam;

[0097] The temperature of the spinning beam is 275°C; the spinning assembly pressure of the spinning beam is 9 MPa.

[0098] A saturated superheated steam device and a monomer suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled to be 160°C, the pressure of the saturated superheated steam device is controlled to be 1.4 bar, and the pressure of the monomer suction device is controlled to be 0.60 MPa;

[0099] The drafting process adopts two pairs of drafting rollers, and the nascent yarn after oiling is first fed into a G1 drafting roller, and then is drafted between a G2 drafting roller and the G1 drafting roller for heat setting, wherein the speed of the G1 drafting roller is 3200 m / min; the speed of the G2 drafting roller is 4900 m / min; the draft ratio is 1.53; the heat setting temperature is 160°C; and the winding speed is 4880 m / min.

[0100] The annual output of the melt-spun polyamide 56 fully-drawn yarn described in the embodiment can reach 15,000 tons per line, the spinning position is 48 positions per line, and the number of spinning heads is 24 heads per position.

[0101] Example 3: 78 dtex / 68 f melt-spun polyamide 56 fully-drawn yarn

[0102] (1) pentanediamine, adipic acid, and water are used to prepare a polyamide 56 salt solution, and then the polyamide 56 salt solution is subjected to pre-polymerization, flashing, and polycondensation to obtain a polyamide 56 melt;

[0103] The molar ratio of the pentanediamine and the adipic acid is 1.05:1; the concentration of the polyamide 56 salt solution is 57 wt%; and the pH value of the polyamide 56 salt solution is 8.0;

[0104] The pressure of the pre-polymerization is 1.7 MPa, and the temperature is 255°C;

[0105] The pressure of the polycondensation is -0.04 MPa, and the temperature is 280°C;

[0106] The polyamide 56 melt is a bright melt, and the titanium dioxide content of the polyamide 56 melt is 0;

[0107] The relative viscosity of the polyamide 56 melt is 2.65; the terminal amino group content is 50 mmol / kg; and the equilibrium moisture content is 450 ppm.

[0108] (2) The polyamide 56 melt obtained in step (1) is subjected to a melt booster pump, a melt filter, a melt conveying pipe, and a spinning beam to form a nascent yarn, and the nascent yarn is subjected to cooling, oiling, drafting, heat setting, and winding to obtain a melt direct spinning polyamide 56 fully drawn yarn.

[0109] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 22 min; the temperature of the melt conveying pipe is controlled to be 282℃; and the dynamic viscosity of the polyamide 56 melt from the melt booster pump to the spinning beam is controlled to be 240 pa*s.

[0110] The temperature of the spinning beam is 280℃; and the spinning assembly pressure of the spinning beam is 14 MPa.

[0111] A saturated superheated steam device and a monomer suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled to be 140℃, the pressure of the saturated superheated steam device is controlled to be 1.5 bar, and the pressure of the monomer suction device is controlled to be 0.70 MPa.

[0112] The drafting process adopts two pairs of drafting rollers, and the nascent yarn after oiling is first fed into a G1 drafting roller, and then is subjected to drafting and heat setting between a G2 drafting roller and the G1 drafting roller, wherein the G1 drafting roller speed is 3300 m / min; the G2 drafting roller speed is 5000 m / min; the drafting multiple is 1.53; the heat setting temperature is 150℃; and the winding speed is 4980 m / min.

[0113] The annual output of the melt direct spinning polyamide 56 fully drawn yarn described in the embodiment can reach 20,000 tons / line, the spinning position is 48 positions / line, and the number of spinning heads is 24 heads / position.

[0114] Example 4: Bright 110 dtex / 68f melt direct spinning polyamide 56 fully drawn yarn

[0115] (1) Preparing a polyamide 56 salt solution from pentanediamine, adipic acid, and water, and then obtaining a polyamide 56 melt through prepolymerization, flashing, and polycondensation;

[0116] The molar ratio of the pentanediamine and the adipic acid is 1.04:1; the concentration of the polyamide 56 salt solution is 55 wt%; and the pH value of the polyamide 56 salt solution is 7.8.

[0117] The pressure of the prepolymerization is 1.75 MPa, and the temperature is 253℃.

[0118] The pressure of the polycondensation is -0.05 Mpa, and the temperature is 282℃;

[0119] The polyamide 56 melt is a bright melt, and the titanium dioxide content is 0;

[0120] The relative viscosity of the polyamide 56 melt is 2.8, the terminal amino group content is 49 mmol / kg, and the equilibrium moisture content is 500 ppm.

[0121] (2) The polyamide 56 melt obtained in step (1) is sent to a spinning beam through a melt booster pump, a melt filter and a melt conveying pipeline to form a primary filament, and the primary filament is cooled, oiled, drawn, heat set and wound to obtain a melt direct spinning polyamide 56 fully drawn yarn.

[0122] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 23 min, the temperature of the melt conveying pipeline is controlled to be 280℃, and the dynamic viscosity of the polyamide 56 melt from the melt booster pump to the spinning beam is controlled to be 250 pa*s.

[0123] The temperature of the spinning beam is 282℃, and the spinning assembly pressure of the spinning beam is 13 MPa.

[0124] A saturated superheated steam device and a monomer suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled to be 140℃, the pressure of the saturated superheated steam device is controlled to be 1.5 bar, and the pressure of the monomer suction device is controlled to be 0.70 MPa.

[0125] The drawing process adopts two pairs of drawing rollers, and the oiled primary filament is first fed into a G1 drawing roller, and then drawn and heat set between a G2 drawing roller and the G1 drawing roller, wherein the G1 drawing roller speed is 3200 m / min, the G2 drawing roller speed is 4800 m / min, the draw ratio is 1.5, the heat setting temperature is 160℃, and the winding speed is 4770 m / min.

[0126] The annual output of the melt direct spinning polyamide 56 fully drawn yarn described in the embodiment can reach 30,000 tons per line, the spinning position is 48 positions per line, and the number of spinning heads is 24 heads per position.

[0127] Example 5: Semi-dull 44 dtex / 48 f melt direct spinning polyamide 56 fully drawn yarn

[0128] (1) Prepare a polyamide 56 salt solution from pentanediamine, adipic acid and water, and then obtain a polyamide 56 melt through prepolymerization, flashing and polycondensation;

[0129] The molar ratio of the pentanediamine and adipic acid is 1.06:1; the concentration of the polyamide 56 salt solution is 58 wt%; the pH value of the polyamide 56 salt solution is 7.5;

[0130] The pressure of the prepolymerization is 1.6 Mpa, and the temperature is 245℃;

[0131] The pressure of the polycondensation is -0.06 Mpa, and the temperature is 273℃;

[0132] The polyamide 56 melt is a semi-dull melt, and the titanium dioxide content is 0.32 wt%; the titanium dioxide is added in the flash process, and the dispersion particle size of the titanium dioxide in the polyamide 56 melt is 0.1-0.6 μm, the particle size distribution ratio of the titanium dioxide with a dispersion particle size of 0.2-0.4 μm is 98.5%, and the particle size distribution ratio of the titanium dioxide with a dispersion particle size of 0.2-0.3 μm is 97.4%;

[0133] The relative viscosity of the polyamide 56 melt is 2.53; the terminal amino group content is 46 mmol / kg; and the equilibrium moisture content is 380 ppm.

[0134] (2) The polyamide 56 melt obtained in step (1) is sent to a spinning beam through a melt booster pump, a melt filter, and a melt conveying pipeline to form a primary filament, and the primary filament is cooled, oiled, drawn, heat set, and wound to obtain a melt direct spinning polyamide 56 fully drawn yarn.

[0135] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 26 min; the temperature of the melt conveying pipeline is controlled to be 272℃; and the dynamic viscosity of the polyamide 56 melt is controlled to be 220 pa*s from the melt booster pump to the spinning beam.

[0136] The temperature of the spinning beam is 272℃; and the spinning assembly pressure of the spinning beam is 13 MPa.

[0137] A saturated superheated steam device and a monomer suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled to be 170℃, the pressure of the saturated superheated steam device is controlled to be 1.2 bar, and the pressure of the monomer suction device is controlled to be 0.65 MPa.

[0138] The drawing process adopts two pairs of drawing rollers, and the oiled primary filament is first fed into a G1 drawing roller, and then drawn and heat set between a G2 drawing roller and the G1 drawing roller, wherein the G1 drawing roller speed is 3000 m / min; the G2 drawing roller speed is 4800 m / min; the draw ratio is 1.6; the heat setting temperature is 155℃; and the winding speed is 4780 m / min.

[0139] The annual output of the melt direct spinning polyamide 56 fully drawn yarn in the embodiment can reach 12000 tons per line, the spinning position is 48 positions per line, and the number of spinning heads is 24 heads per position.

[0140] Example 6: Semi-dull 55 dtex / 51 f melt direct spinning polyamide 56 fully drawn yarn

[0141] (1) pentanediamine, adipic acid and water are used to prepare a polyamide 56 salt solution, and then pre-polymerization, flashing and polycondensation are performed to obtain a polyamide 56 melt;

[0142] The molar ratio of the pentanediamine and the adipic acid is 1.07:1; the concentration of the polyamide 56 salt solution is 61 wt%; and the pH value of the polyamide 56 salt solution is 7.8;

[0143] The pre-polymerization pressure is 1.65 MPa, and the temperature is 248℃;

[0144] The polycondensation pressure is -0.04 MPa, and the temperature is 275℃;

[0145] The polyamide 56 melt is a semi-dull melt, the titanium dioxide content of which is 0.3 wt%; titanium dioxide is added in the flashing process, the dispersion particle size of which in the polyamide 56 melt is 0.1-0.6 μm, the particle distribution ratio of titanium dioxide with a dispersion particle size of 0.2-0.4 μm is 98.0%, and the particle distribution ratio of titanium dioxide with a dispersion particle size of 0.2-0.3 μm is 97.2%;

[0146] The relative viscosity of the polyamide 56 melt is 2.6; the end amino group content is 48 mmol / kg; and the equilibrium moisture content is 480 ppm.

[0147] (2) the polyamide 56 melt obtained in step (1) is subjected to a melt booster pump, a melt filter, a melt conveying pipeline and a spinning beam to form a nascent yarn, and the nascent yarn is subjected to cooling, oiling, drawing, heat setting and winding to obtain a melt direct spinning polyamide 56 fully drawn yarn;

[0148] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 22 min; the temperature of the melt conveying pipeline is controlled to be 273℃; and the dynamic viscosity of the polyamide 56 melt is controlled to be 230 pa*s from the melt booster pump to the spinning beam;

[0149] The temperature of the spinning beam is 273℃; and the spinning assembly pressure of the spinning beam is 12 MPa.

[0150] A saturated superheated steam device and a single suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled at 190℃, the pressure of the saturated superheated steam device is controlled at 1.3 bar, and the pressure of the single suction device is controlled at 0.6 MPa;

[0151] The drawing process adopts 2 pairs of drawing rollers. The oiled nascent yarn is first fed into G1 drawing roller, and then drawn and heat set between G2 drawing roller and G1 drawing roller, wherein the speed of G1 drawing roller is 3300 m / min; the speed of G2 drawing roller is 4900 m / min; the draw ratio is 1.48; the heat setting temperature is 165℃; and the winding speed is 4880 m / min.

[0152] The annual output of the melt direct spinning polyamide 56 fully drawn yarn in the embodiment can reach 15,000 tons per line, the spinning position is 48 positions per line, and the number of spinning heads is 24 per position.

[0153] Example 7: Semi-dull 78 dtex / 68 f melt direct spinning polyamide 56 fully drawn yarn

[0154] (1) Preparing a polyamide 56 salt solution from pentanediamine, adipic acid and water, and then obtaining a polyamide 56 melt through pre-polymerization, flashing and polycondensation;

[0155] The molar ratio of the pentanediamine and adipic acid is 1.06:1; the concentration of the polyamide 56 salt solution is 55 wt%; and the pH value of the polyamide 56 salt solution is 8.2;

[0156] The pre-polymerization pressure is 1.6 MPa, and the temperature is 250℃;

[0157] The polycondensation pressure is -0.03 MPa, and the temperature is 278℃;

[0158] The polyamide 56 melt is a semi-dull melt, the titanium dioxide content of which is 0.32 wt%; the titanium dioxide is added in the flashing process, the dispersion particle size of the titanium dioxide in the polyamide 56 melt is 0.1-0.6 μm, the particle distribution ratio of the titanium dioxide with a dispersion particle size of 0.2-0.4 μm is 98.6%, and the particle distribution ratio of the titanium dioxide with a dispersion particle size of 0.2-0.3 μm is 97.7%;

[0159] The relative viscosity of the polyamide 56 melt is 2.7; the terminal amino group content is 45 mmol / kg; and the equilibrium moisture content is 400 ppm.

[0160] (2) The polyamide 56 melt obtained in step (1) is sent to a spinning beam through a melt booster pump, a melt filter and a melt conveying pipeline to form a nascent yarn, and the nascent yarn is cooled, oiled, drawn, heat set and wound to obtain a melt direct spinning polyamide 56 fully drawn yarn.

[0161] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 20 min; the temperature of the melt conveying pipe is controlled at 276℃; the dynamic viscosity of the polyamide 56 melt is controlled at 240 pa*s from the melt booster pump to the spinning beam;

[0162] The temperature of the spinning beam is 275℃; the spinning assembly pressure of the spinning beam is 14 MPa.

[0163] A saturated superheated steam device and a monomer suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled at 130℃, the pressure of the saturated superheated steam device is controlled at 1.5 bar, and the pressure of the monomer suction device is controlled at 0.7 MPa;

[0164] The drawing process adopts 2 pairs of drawing rollers, and the oiled primary filaments are first fed into the G1 drawing roller, and then drawn and heat set between the G2 drawing roller and the G1 drawing roller, wherein the G1 drawing roller speed is 3300 m / min; the G2 drawing roller speed is 5000 m / min; the draw ratio is 1.52; the heat setting temperature is 170℃; and the winding speed is 4980 m / min.

[0165] The annual output of the melt direct spinning polyamide 56 fully drawn yarn in the embodiment can reach 20,000 tons per line, the spinning position is 96 positions per line, and the number of spinning heads is 12 per position. The gel content in the melt booster pump to the spinning beam is 0.8 wt% per 6 months.

[0166] Example 8: Semi-dull 110 dtex / 68 f melt direct spinning polyamide 56 fully drawn yarn

[0167] (1) Preparing a polyamide 56 salt solution from pentanediamine, adipic acid and water, and then obtaining a polyamide 56 melt through pre-polymerization, flashing and polycondensation;

[0168] The molar ratio of the pentanediamine and the adipic acid is 1.08:1; the concentration of the polyamide 56 salt solution is 58 wt%; and the pH value of the polyamide 56 salt solution is 8.3;

[0169] The pre-polymerization pressure is 1.7 MPa, and the temperature is 254℃;

[0170] The polycondensation pressure is -0.04 MPa, and the temperature is 282℃;

[0171] The polyamide 56 melt is a semi-dull melt, the titanium dioxide content is 0.33wt%; the titanium dioxide is added in the flash process, the dispersed particle size of the titanium dioxide in the polyamide 56 melt is 0.1-0.6μm, the proportion of the particles with the titanium dioxide dispersed particle size of 0.2-0.4μm is 98.3%, the proportion of the particles with the titanium dioxide dispersed particle size of 0.2-0.3μm is 97.2%;

[0172] The relative viscosity of the polyamide 56 melt is 2.82; the terminal amino group content is 50mmol / kg; the equilibrium moisture content is 550ppm.

[0173] (2) The polyamide 56 melt obtained in step (1) is sent to a spinning beam through a melt booster pump, a melt filter and a melt conveying pipeline to form a nascent yarn, and the nascent yarn is cooled, oiled, drawn, heat set and wound to obtain a melt direct spinning polyamide 56 fully drawn yarn.

[0174] The melt residence time of the polyamide 56 melt from the melt booster pump to the spinning beam is 23min; the temperature of the melt conveying pipeline is controlled at 280℃; the dynamic viscosity of the polyamide 56 melt is controlled at 250pa*s from the melt booster pump to the spinning beam.

[0175] The temperature of the spinning beam is 280℃; the spinning assembly pressure of the spinning beam is 15MPa.

[0176] A saturated superheated steam device and a monomer suction device are arranged below the spinning beam, wherein the temperature of the saturated superheated steam device is controlled at 140℃, the pressure of the saturated superheated steam device is controlled at 1.2bar, and the pressure of the monomer suction device is controlled at 0.6MPa.

[0177] The drawing process adopts two pairs of drawing rollers, the oiled nascent yarn is first fed into a G1 drawing roller, and then drawn and heat set between a G2 drawing roller and the G1 drawing roller, wherein the G1 drawing roller speed is 3000m / min; the G2 drawing roller speed is 4800m / min; the draw ratio is 1.6; the heat setting temperature is 165℃; and the winding speed is 4780m / min.

[0178] The annual output of the melt direct spinning polyamide 56 fully drawn yarn described in the embodiment can reach 30,000 tons per line, the spinning position is 96 positions per line, and the number of spinning heads is 12 per position. The gel content from the melt booster pump to the spinning beam is 0.8wt% / 6 months.

[0179] Comparative Example 1: 55dtex / 48f polyamide 56 fully drawn yarn

[0180] The preparation method is same as that of Example 2, except that the polyamide 56 melt obtained in step (1) is first granulated and dried to obtain chips, and the chips are spun to prepare polyamide 56 fully drawn yarns by using a single screw melt to pass through a melt conveying pipeline to a spinning box.

[0181] Half-dull 55 dtex / 51 f polyamide 56 fully drawn yarns

[0182] The preparation method is same as that of Example 6, except that the polyamide 56 melt obtained in step (1) is first granulated and dried to obtain chips, and the chips are spun to prepare polyamide 56 fully drawn yarns by using a single screw melt to pass through a melt conveying pipeline to a spinning box.

[0183] Highly bright 55 dtex / 48 f polyamide 56 fully drawn yarns

[0184] The preparation method is same as that of Example 2, except that the residence time of the polyamide 56 melt from the melt booster pump to the spinning box is 60 min.

[0185] Highly bright 55 dtex / 48 f polyamide 56 fully drawn yarns

[0186] The preparation method is same as that of Example 2, except that the temperature of the melt conveying pipeline is controlled to be 295 ℃.

[0187] Highly bright 55 dtex / 48 f polyamide 56 fully drawn yarns

[0188] The preparation method is same as that of Example 2, except that the dynamic viscosity of the polyamide 56 melt from the melt booster pump to the spinning box is controlled to be 140 Pa·s.

[0189] Table 1: Parameters of polyamide 56 fully drawn yarns prepared in Examples and Comparative Examples

[0190]

[0191] By using the preparation method of the melt direct spinning polyamide 56 fully drawn yarns, by optimizing the melt direct spinning process, controlling the melt residence time, the melt conveying temperature and the dynamic viscosity of the melt and other parameters, not only the production of large capacity polyamide 56 fully drawn yarns can be realized, but also the gel content in the melt booster pump to the spinning box can be effectively reduced.

[0192] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of the preferred embodiments as of their onset and might not represent the scope of the application, and the language sent forth by the claims should be understood to be interpreted in the context of the specification as a whole.

Claims

1. A melt-spun polyamide 56 fully drawn yarn, characterized in that, The fineness of the melt-spun polyamide 56 fully drawn yarn is ≤300 dtex; the breaking elongation of the melt-spun polyamide 56 fully drawn yarn is 40-48%, and the coefficient of variation of the breaking elongation is ≤3.5%; the breaking strength of the melt-spun polyamide 56 fully drawn yarn is 4.0-6.2 cN / dtex, the coefficient of variation of the breaking strength is ≤3.5%, and the yarn unevenness is ≤1.0%. The method for preparing melt-spun polyamide 56 fully drawn yarn includes at least the following steps: passing polyamide 56 melt through a melt booster pump, a melt filter, and a melt conveying pipeline to a spinning box to form nascent yarn; the nascent yarn is cooled, oiled, drawn, heat-set, and wound to obtain melt-spun polyamide 56 fully drawn yarn. The residence time of the polyamide 56 melt from the melt booster pump to the spinning box is 18–30 min, and the temperature of the melt delivery pipeline is 260–290°C; the dynamic viscosity of the polyamide 56 melt from the melt booster pump to the spinning box is ≥200 Pa. s.

2. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, When the polyamide 56 melt is a bright melt, its titanium dioxide content is 0; when the polyamide 56 melt is a semi-dull melt, its titanium dioxide content is 0.25-0.35 wt%.

3. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, When the polyamide 56 melt is a semi-matte melt, its titanium dioxide content is 0.28–0.33 wt%; and / or, The relative viscosity of the polyamide 56 melt is 2.4–3.0; and / or, The polyamide 56 has a melt-terminated amino content of 30–120 mmol / kg; and / or, The equilibrium moisture content of the polyamide 56 melt is 200–1000 ppm.

4. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The relative viscosity of the polyamide 56 melt is 2.45–2.9; and / or, The polyamide 56 has a melt-terminated amino content of 35–100 mmol / kg; and / or, The equilibrium moisture content of the polyamide 56 melt is 300–900 ppm.

5. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The relative viscosity of the polyamide 56 melt is 2.5–2.85; and / or, The polyamide 56 has a melt-terminated amino content of 40–80 mmol / kg; and / or, The equilibrium moisture content of the polyamide 56 melt is 350–850 ppm; and / or, The temperature of the melt conveying pipeline is 265–288°C; and / or, The temperature of the spinning box is 270–292°C.

6. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The relative viscosity of the polyamide 56 melt is 2.55–2.8; and / or, The polyamide 56 has a melt-terminated amino content of 45–60 mmol / kg; and / or, The equilibrium moisture content of the polyamide 56 melt is 400–800 ppm; and / or, The temperature of the melt conveying pipeline is 270–286°C; and / or, The temperature of the spinning box is 273–290°C; and / or, The spinning assembly pressure of the spinning box is 10-25 MPa.

7. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The temperature of the melt conveying pipeline is 273–284°C; and / or, The temperature of the spinning box is 275–288°C; and / or the pressure of the spinning assembly in the spinning box is 12–22 MPa.

8. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, From the melt booster pump to the spinning box, control the dynamic viscosity of the polyamide 56 melt to ≥220 Pa. s; and / or, The temperature of the spinning box is 277–285°C; and / or, The spinning assembly pressure of the spinning box is 14–18 MPa; and / or, A saturated superheated steam device and a monomer suction device are installed below the spinning box.

9. The melt-spun polyamide 56 fully drawn yarn according to claim 8, characterized in that, The temperature of the saturated superheated steam device is controlled to be 90–250°C; and / or, The pressure of the saturated superheated steam device is controlled to be 0.8–3.2 bar; and / or, The pressure of the single-unit suction device is controlled to be ≥0.6MPa.

10. The melt-spun polyamide 56 fully drawn yarn according to claim 8, characterized in that, The temperature of the saturated superheated steam device is controlled to be 120–230°C; and / or, The pressure of the saturated superheated steam device is controlled to be 1.0–2.8 bar; and / or, The pressure of the single-unit suction device is controlled to be ≥0.65MPa.

11. The melt-spun polyamide 56 fully drawn yarn according to claim 8, characterized in that, The temperature of the saturated superheated steam device is controlled to be 130–200°C; and / or, The pressure of the saturated superheated steam device is controlled to be 1.2–2.5 bar; and / or, The pressure of the single-unit suction device is controlled to be ≥0.7MPa.

12. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The drawing process employs two or more pairs of drawing rollers.

13. The melt-spun polyamide 56 fully drawn yarn according to claim 12, characterized in that, The drawing process employs two pairs of drawing rollers. The oiled nascent yarn is first fed into the G1 drawing roller, and then drawn and heat-set between the G2 and G1 drawing rollers.

14. The melt-spun polyamide 56 fully drawn yarn according to claim 13, characterized in that, The speed of the G1 drafting roll is 1800–4200 m / min; and / or, The speed of the G2 drafting roller is 4500–5500 m / min; and / or, The draw ratio is 1.25–2.5; and / or, The heat setting temperature is 140–180°C; and / or, The winding speed is ≥4500m / min.

15. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The initial modulus of the melt-spun polyamide 56 fully drawn yarn is 15–45 cN / dtex; and / or, The boiling water shrinkage rate of the melt-spun polyamide 56 fully drawn yarn is ≤13%; and / or, The dyeing uniformity of the melt-spun polyamide 56 fully drawn yarn is ≥3.5 grade; and / or, The dyeing double-A rate of the melt-spun polyamide 56 fully drawn yarn is ≥96%; and / or, The double A rate of the melt-spun polyamide 56 fully drawn yarn cake appearance is ≥96%.

16. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The unevenness of the melt-spun polyamide 56 fully drawn yarn is ≤0.9%; and / or, The boiling water shrinkage rate of the melt-spun polyamide 56 fully drawn yarn is ≤12.5%; and / or, The dyeing uniformity of the melt-spun polyamide 56 fully drawn yarn is ≥4.0 grade; and / or, The dyeing double-A rate of the melt-spun polyamide 56 fully drawn yarn is ≥97%; and / or, The double-A ratio of the melt-spun polyamide 56 fully drawn yarn in the yarn cake appearance is ≥97%.

17. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The unevenness of the melt-spun polyamide 56 fully drawn yarn is ≤0.8%; and / or, The coefficient of variation of breaking strength of the melt-spun polyamide 56 fully drawn yarn is ≤3.0%; and / or, The boiling water shrinkage rate of the melt-spun polyamide 56 fully drawn yarn is ≤12%; and / or, The dyeing uniformity of the melt-spun polyamide 56 fully drawn yarn is ≥4.5 grade; and / or, The dyeing double-A rate of the melt-spun polyamide 56 fully drawn yarn is ≥98%; and / or, The double A rate of the melt-spun polyamide 56 fully drawn yarn cake appearance is ≥98%.

18. The melt-spun polyamide 56 fully drawn yarn according to claim 1, characterized in that, The unevenness of the melt-spun polyamide 56 fully drawn yarn is ≤0.7%; and / or, The coefficient of variation of breaking strength of the melt-spun polyamide 56 fully drawn yarn is ≤2.5%; and / or, The elongation at break of the melt-spun polyamide 56 fully drawn yarn is 40-45%; and / or, The coefficient of variation of elongation at break of the melt-spun polyamide 56 fully drawn yarn is ≤3.0%; and / or, The boiling water shrinkage rate of the melt-spun polyamide 56 fully drawn yarn is ≤11%; and / or, The dyeing uniformity of the melt-spun polyamide 56 fully drawn yarn is ≥4.7 grade; and / or, The dyeing double-A rate of the melt-spun polyamide 56 fully drawn yarn is ≥99%; and / or, The double A rate of the melt-spun polyamide 56 fully drawn yarn cake appearance is ≥99%.

Images